Paramoeba

Entities that have been assigned to five of the six species of
Paramoeba have been examined with
the electron microscope. No information is available for specimens
assigned to P. schaudinni de Faria et al. The original
description of this species is vague, and it may never to be possible to
know for sure whether an amoeba in hand is the same one that de Faria and
colleagues studied. Moreover, the "species" assigned on the basis of
morphology and ultrastructure may or may not accurately reflect the
situation in nature (more on this topic in the Taxonomy and nomenclature section).
CELL SURFACE. The species are not all alike. The type species,
P. eilhardi, has a single layer of scales that covers the entire
cell surface. The scales are made of organic materials, without any sign
of mineralization (they do not contain carbonates or silicates). Each
scale has an ellipsoidal base that adheres to the cell surface. From
this base, several vertical elements ("columns") arise that support a
simple rim. There are usually eight, but may be as many as fourteen,
columns. The scales are formed in the Golgi apparatus.

The two species P. pemaquidensis and P. aestuarina have a
surface coat that consists of tiny discrete bodies termed
"glycostyles". The glycostyles are organic (not mineralized), cover the
entire cell surface, and appear to be formed in the Golgi. They may
sometimes appear to be hexagonal in outline, and are seldom taller than
broad. Some but not all strains of P. pemaquidensis and
P. aestuarina also have hairlike filaments that arise from the
cell membrane.

No surface coat has been found in the parasitic species
P. invadens and P. perniciosa.

PARASOME. The parasome is bounded by two membranes. Within these
membranes
there are three distinct structures that are also bounded by two
membranes: two peripheral bodies and one central body. These are the
structures within the parasome that show the positive reaction to
DNA-binding dyes and fluorochromes. There is a limited amount of
cytoplasm within the parasome that is not contained within either the
peripheral or the central bodies.

OTHER ORGANELLES. As far as is known, all species of
Paramoeba have one nucleus
per cell. The nucleus has a single, centrally located, essentially
spherical nucleolus.

Each cell has several sausage-shaped, unbranched mitochondria. The
cristae are tubular.

The finger-like pseudopodia ("dactylopodia")
may have a central core of fine fibrils. Such fibrils are not commonly
observed in other amoebae. The composition and function of these fibrils
is not known.